A dengue virus infection has, as a specific infection, the highest incidence rate next to the world's three big infectious diseases (AIDS, malaria and tuberculosis) and spreads globally.
Dengue virus is single-stranded RNA virus belonging to Flavivirus family and has four serotypes distinct in their antigenicity. It is perceived that once infection occurs with a certain serotype of dengue virus, reinfection of the same serotype of dengue virus will never occur for almost lifelong period due to acquired immunity. However, cross protection against different serotypes continues only for about 12 weeks at the longest and therefore dengue virus infection can occur twice or more. In particular, it is known that “dengue hemorrhagic fever” and “dengue shock syndrome”, which are severe clinical conditions sometimes leading to death, likely occur at the second or later infections.
For dengue infection, there is no established therapy and its prevention is limited. Under existing conditions, countermeasures against infection are to expel mosquitos and to improve environments, and to guide for the use of repellent and appropriate clothes on a personal level. However, these measures are not sufficient in view of cost and effect. Therefore, prevention of infection or prevention of incidence by a vaccine is desired which can be inoculated in a wide age range and exhibits excellent efficacy.